Silicone gums generally consist of linear chains of poly(dimethylsiloxane) that typically possess kinetic viscosities greater than one million cSt at 25° C. Silicone gum emulsions are important in the coatings industry as they function as slip and anti-mar additives for both aqueous and non-aqueous coatings. An important industrial application of silicone gum emulsions is as “band ply lubricants,” used in the manufacture of tires.
Preparation of aqueous mechanical emulsions of silicone gum is difficult due to the handling of such highly viscous materials. These emulsions are typically prepared using a specialized surfactant based on a siloxane copolymer resin. U.S. Pat. No. 4,125,470 to Fenton and Keil describes representative emulsions of this type. A drawback to these types of emulsions is that they contain xylene and other undesirable substances that are present during the manufacture of the siloxane copolymer resin. The presence of xylene in the band ply lube products also precludes their use in personal care applications.
Silicone gum can be emulsified using specialized equipment such as a twin screw extruder (TSE). However, the costs for such equipment are relatively high, both from a capital and an operational standpoint.
Thus, there exists a need to identify processes to prepare mechanical emulsions of silicone gums that do not require specialized surfactants containing aromatic solvents, nor require expensive emulsification equipment.